Eastern Pacific Tropical Discussion

Active Tropical Systems Basin Outlooks Satellite
Eastern Pacific Basin Tropical Discussion
 
597 
AXPZ20 KNHC 260950
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Mon Sep 26 2016

Tropical weather discussion for the eastern Pacific Ocean from
the Equator to 32N, east of 140W. The following information is
based on satellite imagery, weather observations, radar, and
meteorological analysis.

Based on 0600 UTC surface analysis and satellite imagery through
0945 UTC.

...SPECIAL FEATURES...

Tropical Storm Roslyn centered at 16.8N 119.5W at 27/0900Z, or
about 750 nm wsw of the southern tip of the Baja California
Peninsula, moving n-ne or 020 degrees at 4 kt. Estimated minimum
central pressure is 1005 mb. Maximum sustained wind speed is 35
kt with gusts to 45 kt. Currently, scattered moderate isolated
strong convection is observed over the se semicircle, within 120
nm either side of a line from 19n116W to 12N120W. Roslyn is
forecast to maintain minimum tropical storm strength through
late Tue, then lose tropical characteristics on Tue night with a
30 kt remnant low pres near 20.4N 117.0W at 06 UTC Sep 28. The
remnant low will continue to gradually weaken late in the week.
Refer to the latest NHC forecast/advisory under AWIPS/WMO
headers WTPZ23 KNHC/TCMEP3, or visit the NHC website at
http://hurricanes.gov for additional details.

...TROPICAL WAVE...

A tropical wave is analyzed to the n of 08N along 99W and has
been drifting westward. Scattered moderate to strong convection
is noted w of the wave within 30 nm of the Pacific coast of
Mexico between 97W and 101W.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... 

The monsoon trough extends w off the Pacific coast of northern
Costa Rica at 11N85W to 11N96W, then dips sw to 10N112W where it
loses identity. Scatterometer winds indicate that the monsoon
trough resumes just sw of T.S. Roslyn at 14N122W, and continues
wsw to the 1008 mb surface low previously mentioned near
11.5N139W.

Scattered moderate isolated strong convection is observed within
120 nm of 08N85W. Isolated moderate and strong convection is
noted elsewhere within 180 nm either side of a line from 06N82W
to 11N100W to 08N109W, and from 07N to 14N between 120W and 137W.

...DISCUSSION...   

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

A sub-tropical ridge axis extends from nw to se across the
offshore zones w of the Baja Peninsula terminating near 22N110W.
Light to gentle nw winds are observed w of the Baja Peninsula
with little change expected through tonight, then the gradient
should further relax supporting light n to ne winds through late
Tue. Gentle to occasionally moderate flow expected elsewhere
along the Pacific coast of Mexico through tonight. Thereafter,
the remnants of Roslyn will spread n across the extreme western
waters of offshore zones PMZ015 and PMZ013 from Tue through Wed
night, with a strong ne to e to se wind shift, and seas to a max
of 11 ft.  

Moderate to fresh nw winds are expected across the northern Gulf
of California this morning, then the gradient will relax
supporting light and variable winds through Tue night, then
becoming light n winds throughout the entire gulf waters on Wed.
 
A cold front will pass through the sw Gulf of Mexico early this
week, resulting in strong drainage flow across the Gulf of
Tehuantepec beginning Wed night, and then pulsing through the
upcoming weekend. Guidance has backed off on the winds reaching
gale force.  

OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND
WITHIN 750 NM OF ECUADOR...

Light to gentle southerly winds expected n of about 05N, while
gentle to locally moderate s to sw flow is expected s of 05N
through the middle of the week. Combined seas of 3 to 6 ft
primarily in mixing long-period sw and nw swell are expected
this week.

REMAINDER OF THE AREA... 

A 1008 mb low pressure is embedded in the monsoon trough near
11.5N140W. Scattered moderate isolated strong convection is
noted within 120 nm either side of a line from 09.5N138W to
13N140W with banding features se of the center. The low is
forecast to move w and become quasi-stationary near 13N142W late
tonight, then move n during mid week accompanied by strong winds
over its e semicircle that will spread e into the discussion
area near 13N139W on Wed, surrounded by a larger area of 7 to 9
ft seas across the discussion waters from 11N to 17N w of 136W.
Atmospheric and oceanic conditions will become more favorable
for tropical cyclone formation in 3 to 5 days.   
     
$$
Nelson